Characterization of carbon materials with the help of NMR methods

Combined NMR cryoporometry, relaxometry and diffusometry were applied to characterize porous carbon materials. Pore space characterization in NMR cryoporometry is based on the measurement of melting point depression of the confined liquids, whereas NMR relaxometry and diffusometry explore the random motion of the molecules under confinement by the pore space. We demonstrate compatibility between the evidence of classical sorption experiments and NMR cryoporometry on pore size distribution. There is a distribution in both the nuclear magnetic relaxation rates and diffusion coefficients. These distributions have to be referred to heterogeneities in the pore space. Since they can only be observed if their influence is not averaged out on the diffusion paths covered by the molecules during the respective measurements, the spatial extension of the regions with structural differences (as evidenced by the differences in diffusion and nuclear magnetic relaxation of the probe molecules) may be estimated to be at least of the order of 20 μm.